There has been a massive outcry over the detention of Guardian journalist Glenn Greenwald's partner David Miranda by British airport authorities, but is all the outrage a tad overdone?

On Sunday, British authorities detained Miranda for nine hours. The Guardian reported, and UK authorities subsequently confirmed, that he had been detained by British authorities under an anti-terrorism law while he was in transit from Berlin to Brazil and changing planes at London's Heathrow Airport. Although he was released without charge at the end of the nine hours, all of his electronic equipment, including his laptop computer, memory sticks and cellphone, was confiscated.

In the immediate aftermath of the detention, all of the initial reactions condemned Miranda's detention as an act of blatant intimidation on the part of the British authorities, designed to 'send a message' to Greenwald and ostensibly the Guardian newspaper.

Greenwald embraces Miranda after his arrival in Brazil: Reuters

" Journalist or not, the British government had no right to hold him under a terrorism statute without a scrap of evidence that he was connected to any act of terrorism or any plot", said Andrew Rosenthal writing for the New York Times.

Greenwald for his part, wrote an outraged blog post in which he vowed not to be deterred from reporting aggressively on the truth:

This is obviously a rather profound escalation of their attacks on the news-gathering process and journalism. It's bad enough to prosecute and imprison sources. It's worse still to imprison journalists who report the truth. But to start detaining the family members and loved ones of journalists is simply despotic. Even the Mafia had ethical rules against targeting the family members of people they felt threatened by. But the UK puppets and their owners in the US national security state obviously are unconstrained by even those minimal scruples.

If the UK and US governments believe that tactics like this are going to deter or intimidate us in any way from continuing to report aggressively on what these documents reveal, they are beyond deluded. If anything, it will have only the opposite effect: to embolden us even further.

Later, Keith Vaz, chairman of the Home Affairs Select Committee, and shadow home secretary Yvette Cooper said police had to explain why terrorism powers were used to detain Miranda. "Bearing in mind it is a new use of terrorism legislation to detain someone in these circumstances... I will write to the police to ask for the justification of the use of terrorism legislation - they may have a perfectly reasonable explanation", the BBC quoted him as saying.

But was there more to the detention of Miranda than mere intimidation? Here are some facts we may want to consider before we start complaining about mafia tactics.

Miranda was on his way to Brazil after a visit to Laura Poitras, an independent film-maker who was the first journalist to interact with Snowden. Poitras co-authored stories based on Snowden's material for the Washington Post and the German magazine Der Spiegel.

Greenwald himself has told the New York Times that Miranda went to Berlin to deliver materials downloaded by Snowden to filmmaker Poitras and to acquire from Poitras a different set of materials for delivery to Greenwald, who lives with Miranda near Rio de Janeiro.

Reuters further reports that British authorities seized all electronic media, including data memory sticks, material which, as Greenwald cheerily told the Forbes website,"was heavily encrypted." He was, at the end of the day, carrying sensitive information that is illegal to possess. We can argue whether the use of the anti-terrorism law was justified, but the UK government had a clear and legal interest in retrieving leaked classified data -- which seems to be the goal of the detention.

2. Did Miranda really have nothing to do with The Guardian's stories?

One of Greenwald's main grouses with the detention was that Miranda was 'not even a journalist' and should not be interrogated about The Guardian and what stories on the NSA and Snowden they were planning to publish. But a closer look at the facts reveal that Miranda was not just an innocent family member caught up in a government vendetta.

First, The Guardian paid for Miranda's flight. A spokesman for the newspaper confirmed that they had paid for the flight, but asserted that Miranda was not an employee of the newspaper, and instead "often assisted" with Greenwald's work. But Guardian editor Alan Rusbridger has acknowledged Miranda's key role:

In this work he is regularly helped by David Miranda. Miranda is not a journalist, but he still plays a valuable role in helping his partner do his journalistic work. Greenwald has his plate full reading and analysing the Snowden material, writing, and handling media and social media requests from around the world. He can certainly use this back-up.

Reuters also reported that Miranda, along with Greenwald had met face to face in Hong Kong with Snowden and has written or co-authored many of the newspaper's stories based on his material. It's a bit much then to claim that Miranda was just a member of Greenwald's family.

While the reasons for Miranda's detention may not be quite as 'illegitimate' as critics claim, there are very troubling aspects to the way he was held. He was detained under schedule 7 of the Terrorism Act 2000 which allows police to hold someone at an airport for up to nine hours for questioning about whether they have been involved with acts of terrorism. Anyone detained must "give the examining officer any information in his possession which the officer requests". Any property seized must be returned after seven days.

Why, however, was he detained for nine long hours?

Dr David Lowe, a former counter-terrorist detective told the BBCthat the length of the detention might be explained by the "volume of documentation" carried by Miranda. "He said the amount of information revealed by Mr Snowden to the Guardian was not yet known, but police might have kept Mr Miranda for the full nine hours allowed because they had lots of data to go through. Dr Lowe also said Mr Miranda might have been targeted because of the "top secret" information police thought he was carrying, rather than because of his relationship with Mr Greenwald", the BBC report added.

This then may be the most worrying aspect of Miranda's detention, which bodes ill for any news outlet committed to serious investigative journalism. One US security official told Reuters that one of the main purposes of the detention was to send a message to recipients of Snowden's materials, including the Guardian, that the British government was serious about trying to shut down the leaks -- the kind of seriousness they displayed when they came into the Guardian's office to destroy all hard drives containing classified information.

Alan Rusbridger of The Guardian writes in this op-ed, that the arrest of Miranda could have far reaching consequences for journalism as a whole.

We are not there yet, but it may not be long before it will be impossible for journalists to have confidential sources. Most reporting – indeed, most human life in 2013 – leaves too much of a digital fingerprint. Those colleagues who denigrate Snowden or say reporters should trust the state to know best (many of them in the UK, oddly, on the right) may one day have a cruel awakening. One day it will be their reporting, their cause, under attack. But at least reporters now know to stay away from Heathrow transit lounges.